The present invention relates generally to computer systems having a display device, and in particular to removing a current display device from the computer system and connecting a new display device to the computer system during operation of the computer system.
Typical prior art computer system has a display device or CPU (central processing unit) operatively connected to a system memory and to a graphics card or video board. A display device is then connected to the graphics card or video board in order to display images supplied by the CPU. A configuration of the computer system refers to the assortment of components that make up the system and their interconnection. Configuration can refer to either hardware or software or the combination of both. For example, a typical configuration for a personal computer consists of a main system memory, a floppy drive, a hard drive, a modem, a CD ROM drive, a monitor of display device, and an operating system. Many software applications require that the computer system have a certain minimum configuration, for example, software that requires graphics display monitor and a video adapter, a particular microprocessor, and a minimum amount of main system memory.
It is well known in the prior art that when a new device or program is installed in the computer system, the system must be reconfigured. This means that certain switches and jumpers must be set for hardware, or new values must be defined for parameters for software. The video adapter is a board that plugs into the computer to give it display capabilities. Obviously, the display capabilities are a function of the display device, which is connected to the video adapter. Adapters offer different types of video modes, the two basic categories of video modes being text and graphics. Also, display devices typically offer a choice of resolutions from the image displayed. Video adapters contain their own memory so that the computer system""s main system memory or RAM is not used for storing displays. If the video adapters perform graphics calculations then they have graphics co-processors and are typically referred to as graphics accelerators.
In order for the computer system to recognize the type of display device, which is connected thereto, each display device has what is termed extended display identification data (EDID). The EDID is a VESA standard data format that contains basic information about the display device and its capabilities, including vendor information, maximum image size, color characteristics, factory pre-set timings, frequency range limits, and character strings for the display device name and serial number. This information is stored in the display device and is used to communicate with the system through, typically, a display data channel between the display device and the graphics adapter. The system uses this information for configuration of the system.
In prior art systems there was limited space for storing the EDID in the computer system. During run time of the computer system the BIOS space is write protected and no EDID data can be stored in the BIOS space during run time. Additionally, it takes relatively a long time to read the EDID from the display device. Thus, it cannot be read every time a mode is set since it introduces extremely long periods of time when mode query is done by third party software. In addition, when hot plugging display devices (disconnecting one display device and connecting a different display device during operation of the computer system), the EDID data sizes are not known until actually reading and analyzing the EDID. In the prior art, dynamic allocation of required storage space is impossible.
Therefore, it is a drawback of the prior art that a computer system cannot be readily reconfigured for a different display device during operation of the computer system.